Through a vehicle-mounted head-up display system, a to-be-projected image may be projected onto a front windshield of a vehicle. In the case of observing a road condition, a driver may rapidly read relevant data on a dashboard without changing a focal length of the driver's eyes, so as to improve the driving security. In the related art, the vehicle-mounted head-up display system is installed inside the vehicle, and reflects light beams from a projection device into the vehicle through a conventional catadioptric structure, so as to form a real image of the to-be-projected image.